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Thread: How to do thread communication in java

  1. #1
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    Default How to do thread communication in java

    I have 2 threads and I need one variable get tu dhe second thread.
    For example: main Thread have int i=5;
    and i want this variable to second Thread
    How can i do this?


  2. #2
    Senile Half-Wit Freaky Chris's Avatar
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    Default Re: Thread variable

    Depends what exactly you want to do, perhaps yuo could show us your code so we know what you are doing and how we can work with it.

    Chris

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    Default Re: Thread variable

    Yes ok it is udp server
    /*
     * To change this template, choose Tools | Templates
     * and open the template in the editor.
     */
     
    package msnserver;
     
     
    import java.io.IOException;
    import java.net.DatagramPacket;
    import java.net.DatagramSocket;
    import java.net.InetAddress;
    import java.util.logging.Level;
    import java.util.logging.Logger;
     
    /**
     *
     * @author Lolek
     */
     
    public class Main {
     
        /**
         * @param args the command line arguments
         */
        public static void main(String[] args) {
            vlakno ServerSocket2 = new vlakno();
            ServerSocket2.vlak.start();
              try {
     
                DatagramSocket server = new DatagramSocket(5000);//vytvoreni server soketu ktery naslouchat na portu 5000           
                byte[] poslana = new byte[256];//vytvoreni 256 bytoveho pole pro posilana data
                byte[] prijata = new byte[256];//vytvoreni 256 bytoveho pole pro prijata data             
                byte[] lolo = new byte[256];  
                //BufferedReader cteni = new BufferedReader(new InputStreamReader(System.in));
                //String klavesnice;
                //byte ip[] = { Network.ip(127), Network.ip(0), Network.ip(0), Network.ip(1)};
                //String ukonceni = "/q";
                //String kOdeslani;           
                while (true)                
                {
                DatagramPacket prijatyPaket = new DatagramPacket(prijata,prijata.length);// zaobaleni pole bajtu k prijmu
                server.receive(prijatyPaket);//prijmuti paketu              
                int port1 = prijatyPaket.getPort();//Ziskani portu klienta a prirazeni do port
                InetAddress IPAdresa1 = prijatyPaket.getAddress();
                System.out.println("Port:"+ port1 +"Adresa:"+IPAdresa1);
                //InetAddress adresa = InetAddress.getByAddress(ip);           
                String prepos = new String(prijatyPaket.getData()); 
                System.out.println(prepos);
                lolo = prepos.getBytes();    
                DatagramPacket klient1 = new DatagramPacket(lolo,lolo.length,IPAdresa1,port1);
                server.send(klient1);        
                //klavesnice = cteni.readLine();
                //poslana = klavesnice.getBytes();
                //DatagramPacket klv = new DatagramPacket(poslana,poslana.length,IPAdresa1,port);
                //server.send(klv);
                }            
            } catch (IOException ex) {
                Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
            }    
     
        }
     
    }
    class vlakno implements Runnable
    {
        Thread vlak;
        vlakno()
        {
        vlak = new Thread(this,"Vlakno 2");
        }
       public void run ()
        {   
     
            try 
            {
                DatagramSocket server2 = new DatagramSocket(4000);
                byte[] prijata = new byte[256];
                byte[] odeslana = new byte[256];
                byte[] ip ={Network.ip(192),Network.ip(168),Network.ip(1),Network.ip(101)};
                int port2; 
     
     
                while(true)
                {
                 DatagramPacket prijatyPaket2 = new DatagramPacket(prijata,prijata.length);
                 server2.receive(prijatyPaket2);
                 port2 = prijatyPaket2.getPort();
                 InetAddress IPAdresa2 = prijatyPaket2.getAddress();
                 String prijaty = new String(prijatyPaket2.getData());
                 odeslana = prijaty.getBytes();
                 DatagramPacket odesilanyPaket2 = new DatagramPacket(odeslana,odeslana.length,IPAdresa2,port2);
                 server2.send(prijatyPaket2);
                }            
            } 
            catch (IOException ex) 
            {
                Logger.getLogger(vlakno.class.getName()).log(Level.SEVERE, null, ex);
            }    
        }
    }
    And i need change from first thread get IP address and get port, to second thread. Client send datagram to server and server send this datagram to another client.

  4. #4
    mmm.. coffee JavaPF's Avatar
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    Default Re: Thread variable

    If you want to make the variable available outside of the main method then declare it as:

    public static int i=5;
    Just after

    public class Main {

    Then you can access it anywhere. For example,

    int newInt = i;

    I'm not sure if this is what you mean though?!
    Please use [highlight=Java] code [/highlight] tags when posting your code.
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  5. #5
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    Default Re: Thread variable

    No i need when one thread get these getPort and getAddress give to second thread. first client send gatagram to server, server getAddress and getPort and these give to second thread this thread recive datagram for another client and send this datagram first client becouse this thread know address and port.

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